Design and tests of the soil moving and leveling blade roller for combined tilling machines

Combined tillage can be utilized to implement two or more tillage operations in the field at the same time. The efficient and potential way can be widely used to reduce soil compaction, labor, and fuel cost. However, the current combined tilling machine cannot fully meet the harsh requirement of better surface flatness and soil distribution after stubble breaking and burying operation. In this study, a piecewise anti-helix blade roller was designed to improve the parameter robustness using Taguchi method and discrete element simulation. Firstly, the structural scheme of moving and leveling soil blade rollers was designed, according to the M-shaped surface produced by the ordinary blade roller in the previous generation prototype test. Specifically, the gearbox was put in the middle of the frame with a blade roller at each side. Each blade roller was designed as two sections with opposite and unequal lengths of spiral directions. As such, the middle and each side ridge ditches were filled for the moving and leveling of the two raised soil ridges that formed by the burying operation. Secondly, some key factors were qualitatively analyzed to optimize the work parameters of the piecewise anti-helix blade roller. The specific level of the factor was determined in the axial soil transportation and throwing off the blade roller. Taguchi method was used to design the test scheme, where the surface flatness was taken as the optimization objective, and the sandy loam and clay loam were the noise factors. The three-dimensional models were established using the test parameters after the discrete element simulation. The optimal combination of parameters was obtained suitable for the different soil types. Specifically, the cutter shaft speed and diameter, the screw angle, and the blade seat spacing were 300 r/min, 80 mm, 70°, and 62 mm, respectively. The blade roller structure was the double helix mode, with the rotary blade model of IT245. The soil operation was then simulated under the optimal combination in the farm test field. The surface flatness was achieved at 14.2mm, indicating the robustness of the optimal parameter of the blade roller. Finally, the prototype was manufactured with the optimal combination of parameters, and then verified by the field test. After that, the surface flatness, soil distribution uniformity, stability coefficient of rotary tillage depth, and soil breaking rate were 11.6 mm, 92.6%, 93.2%, and 86.4%, respectively, which were better than the requirements of wheat cultivation for the tillage and land preparation. The better performance of the blade roller was achieved under the optimal combination of parameters. The finding can provide a promising approach to designing the blade roller in a combined tilling machine.